This invention is related generally to surveillance systems, and more particularly to a method of storing digital video captured by an in-car video system.
Vehicle-mounted surveillance systems, also termed in-car video systems, are seeing increased use in the security industry and law enforcement community as an effective means to provide an indisputable video and audio record of encounters involving officers and citizens. In these systems, a video camera is typically mounted on the police car's dashboard or windshield and is generally arranged to have a field of view of the area to the immediate front of the car. The field of view approximately corresponds to what an officer would see when seated in the car's front seat. The video camera is operably coupled to a recording device, such as a video cassette recorder (“VCR”) or digital video recorder (“DVR”), mounted in the police car, often in the trunk.
In-car video systems generally employ a wireless microphone carried on the person of a law enforcement officer to record an audio soundtrack that accompanies the visual scene captured on the video recording. The audio soundtrack is an extremely valuable complement to the recorded video because it acts as a transcript of what was said, by whom and when. In some cases, the audio soundtrack is more valuable as evidence than the visual record because issues pertaining to consent, admissions, and state-of-mind of the suspect and/or officer (to cite just a few examples) may be resolved more effectively by the audio record. In some systems, additional wired microphones may be deployed in other locations within the car, such as the rear-seat passenger area, to record sounds and conversations emanating from those locations.
A video recording may be started manually by the officer, or in some systems, the video recording is started automatically when, for example, the officer activates the police car's emergency systems (such as overhead lights and/or sirens), vehicle doors are opened, or when a vehicle speed-measuring radar unit is operated. The incident is recorded on video until the system is either manually or automatically switched off.
In-car video systems serve to enhance prosecution of traffic, DWI/DUI and controlled dangerous substances offenses (to name just a few) by contributing detailed graphical and auditory evidence in a time-sequential manner that is inherently unbiased and objective. Such evidence is a valuable adjunct to eyewitness and officer testimony. In addition, as with other quality-improvement initiatives where conduct is surveyed and recorded, in-car video system usage has been shown to assist in the maintenance of high professional standards among law enforcement personnel. Police-community relations have improved and citizen complaints of police misconduct have lessened in many jurisdictions where in-car video systems are used, often as a result of the inherently high-quality evidence provided by such systems. Videos taken with in-car video systems are also valuable training aids to law enforcement personnel.
Video evidence is protected (and the evidentiary chain of custody readily established) because the video recorder and video recording medium are typically “locked”, often both mechanically and electronically, within a tamperproof security enclosure in the car (e.g., the trunk) that is only accessible by law enforcement command personnel. In addition, the in-car systems are configured to prevent erasure or over-recording of a recorded incident to ensure the integrity of the video evidence. In-car video systems may superimpose time and date stamps on the recorded video image as a further enhancement to the evidentiary strength of the video recording. In addition to date and time, other data, collectively referred to as “incident markers” such as the indication of the use of emergency lights and sirens, door opening and closures, vehicle speeds and other indicators may be recorded.
In-car video systems have historically been based on analog videotape technology. All video and audio sources (i.e., camera and microphones) are thus recorded on videotape. Once that videotape is full, it is removed and stored for a period of time determined by the requirements of the particular police department. That period may be days, weeks or years. As a result, even a small department may face storing a large number of tapes, perhaps several thousand or more, at any given time. Larger departments face an even larger tape storage problem.
While current videotape-based in-car video systems perform very well in many applications, digital video recording technology—where video is recorded to a computer-type media such as a hard disk drive by a DVR—may be utilized in other applications to realize several potential advantages. These include, for example, the ability to access (and very rapidly) any portion of the recording for incident review, improved reliability of digital media compared to tape mechanisms, better and more consistent image quality, and the lack of degradation of new images and audio when recorded over the top of the old ones.
One of the challenges presented from digital video storage is the amount of long term storage that is typically required in most applications. For example, one hour of VHS quality full motion, 30 frames per second, video requires approximately 1 gigabyte of digital storage. Thus, for each six-hour (i.e., T-120) VHS tape utilized, approximately six gigabytes of digital storage is required. The storage requirements for an agency differ greatly due to the varied length of time the video is required to be held. For example, some agencies save videos for 90 days unless there is an incident associated with the recording. Once the 90 days has elapsed, the videotape is typically erased and reused. Thus, a department with 20 cars producing eight hours of video per day per car would require approximately 14,400 gigabytes of digital storage. Storage requirements of such magnitude have significantly impacted the affordability of digital video recording systems.